The present invention relates to a radio resource management method, management apparatus employing the same, base stations, and terminals. Particularly, the present invention relates to a radio resource management system suitable to public mobile communications of the cellular system or to radio networks such as radio LANs.
In radio networks such as public mobile communications or radio LANs, plural radio base stations, each which has a service area, are installed and data communications and conversation services are provided to radio terminals existing in each of the service areas. In such systems, it is important to manage radio resources. For example, there is the technique of reducing the transmission power of the concerned station when traffic is jammed because of an increased number of radio terminals under command of a radio base station while commanding other neighboring radio base stations to increase the transmission power of a control channel of a local station (refer to patent document 1). According to this technique, the service area of a local station is narrowed while the service area of a neighboring radio base station is expanded. Thus, the radio terminals under the local station are transferred to the neighboring radio base station, so that load distribution is urged.
Furthermore, the radio resource management technique has been proposed that a radio base station autonomously optimizes its transmission power based on both information on location of a neighboring radio base station and measured traffic volumes (refer to non-patent document 1).
Moreover, as the system of managing radio resources in cooperation with a radio base station and radio terminals, the technique has been proposed that a radio base station memorizes link quality statistical information to each radio terminal and preferentially offers other radio base station as a candidate to be transferred (refer to patent document 2).
[Patent Document 1]
JP-P1997-163435A
[Patent Document 2]
JP-P2001-103531A (refer to Pages 2 to 5 and FIG. 1 to FIG. 4)
[Non-Patent Document 1]
“Autonomous cell shaping Method Based on Arrangement of Base stations”, written by Tobe et al, in General Meeting of The Institute of Electronics, Information and Communication Engineers of Japan issued in 2002, B-5-70, Pages 520
According to the patent document 1 and the non-patent document 1, there is the disadvantage in that adjusting the size of a service area based on the number of radio terminals and the traffic volume causes oscillation of the area size. Here, the area size oscillation means that the area size expands and contracts repeatedly. Because a radio terminal can move arbitrarily between areas of radio base stations, variations in the number of mobile terminals or in traffic volume occur very often, so that the transmission power is adjusted for each movement. As a result, oscillation of the area size occurs and makes it difficult to effectively control the radio resources.
In the system according to the patent document 2, the radio resources are managed in cooperation with radio base stations and radio terminals. For that reason, both the radio base station and the radio terminal require hardware and software additionally modified for radio resource control. Hence, the problem is that the radio resources cannot be effectively managed.